Automatic gain control or AGC systems are known and widely used. However present communications systems being developed and proposed, such as frequency hopped systems where the channel frequency varies relatively often or time division multiple access systems where a receiver must acquire the signal quickly and relatively often can present unique problems. These problems may be exacerbated where a particular received or on-channel signal can be relatively narrow in bandwidth. Conventional AGC systems normally operate primarily on an on-channel signal to control receiver gain in order to establish an appropriate on-channel signal level. Unfortunately, the required fast attack times necessitated with rapid frequency changes or time slotted periods of receiver activity can be at odds with the response times for conventional on-channel AGC systems.
Receiver architectures are evolving and due in part to economic pressures, less selectivity is being incorporated in receiver front ends and intermediate frequency (IF) stages. Practitioners are opting instead to incorporate the selectivity in later digital processing stages. Unfortunately that means a broader band of signals may be present in the front ends, IF stages, or analog to digital converter(s) (ADC) (used to convert from analog received signals to the digital domain). The chances that the front ends and particularly later receiver stages such as IF stages or ADCs may be overloaded by a large wideband (on-channel and adjacent or near channel signals has increased with this reduction in front end selectivity. This may cause overloading conditions (exceeding dynamic range) for cost effective ADCs and additional time delays for on-channel AGC systems to operate.